A study suggests that Mexican American women diagnosed with an aggressive type of breast cancer are more likely than African American women diagnosed with the same type of breast cancer to have a family history of breast cancer. The association between the aggressive breast cancer and family history suggests that abnormal breast cancer genes may be more common in Mexican American women.

The study also found that Mexican American women were more likely to have the breast cancer found by breast self-exam rather than by mammogram.

The study, called the ELLA Binational Breast Cancer Study, interviewed more than 650 women of Mexican descent diagnosed with invasive breast cancer. About half of the women lived in the United States and the other half lived in Mexico. The researchers compared the details about each woman's diagnosis, risk factors, and health behaviors to the same information from African American women diagnosed with breast cancer.

The results:

There seemed to be a link between a family history of breast cancer and being diagnosed with triple-negative breast cancer (cancer that is estrogen-receptor-negative, progesterone-receptor-negative, and HER2-negative) in Mexican American women. This link doesn't seem to happen in African American women. Still, the link was influenced by where the Mexican American women lived. The link between family history and triple-negative breast cancer was strong in Mexican American women living in Arizona. But the link wasn't as strong in Mexican American women living in Texas. This difference might be because the women in these two states came from different populations in Mexico.

Even though 72% of the Mexican American women had regular mammograms before being diagnosed with breast cancer, only 22% of the cancers were found by mammogram. Most of the women (68%) said that something they found during a breast self-exam led to diagnosis. It's not clear why this happened. Breast cancer found by self-exam is usually larger than a cancer found by mammogram, which may suggest that Mexican American women may be more likely to be diagnosed with later-stage breast cancer, which may be harder to treat.

Almost half of the Mexican American women said they waited at least a month to see a doctor after they found a change in their breasts. About a third of these women said they waited to see a doctor because they didn't have health insurance or couldn't pay for health care. Another third said they didn't think the changes in their breasts were important at first. Other reasons for waiting to see a doctor included fear of a breast cancer diagnosis and difficulty making an appointment.

Research on breast cancer specifically in Mexican American and other Hispanic/Latina women has been done less often than research on breast cancer in white and African American women. Research such as the study reviewed here, sometimes called a population study, can help doctors identify patterns of diseases, such as breast cancer, in different groups of people. Population studies also can help explain differences in disease rates or types in different ethnicities of people.

It's good that mammogram rates were high among the Mexican American women in this study. Still, it's troubling that many of the women who found a change in their breasts during self-exam waited a month or more to see a doctor. If you find a change in your breast, talk to your doctor right away. DON'T WAIT. Help is available if you don't have insurance or can't afford the care you need. The thought of cancer is scary, but don't let fear stop you from seeing a doctor. There is only one of you and you deserve the best and most timely care possible.